Subsidence of organic soils in the everglades agricultural area during the past 19 years

The Everglades Agricultural Area (EAA) is a highly productive agricultural region, yielding 22% of the sugar produced in the U.S., several winter vegetables, rice, and sod. The organic soils of the EAA are the foundation of this agricultural productivity. For approximate to 5000 years prior to its drainage and conversion to an agricultural region, most of the organic soils in the EAA accreted at the rate of approximate to 0.08 cm yr(1). Since drainage in the early part of this century, however, most of these soils have been subsiding at rates of 2.5 to 3.0 cm yr(1). From the early 1900s through 1978, the rate of soil subsidence was monitored along several subsidence transects, The purpose of this study was to resume that monitoring along eleven of the major transects. Soil along each of the eleven transects was measured at intervals of 7.62 to 15.24 m. Also, the horizontal position of each transect was established using Global Positioning System (GPS) technique. Our measurements indicated that the rate of subsidence in the EAA from 1978 through 1997 had decreased to no more than 1.45 cm yr(1). Since 1978, therefore, approximate to 27 cm of soil has been lost due to subsidence. However, had the subsidence rate continued at 2.54 cm per year, an additional 21 cm or a total of 48 an of soil would have been lost during the same time period. Growers are to be commended for this substantial soil conservation effort. This reduced rate of soil subsidence not only prolong their agriculture, but also has positive ecological and hydrological implications for the Everglades region. Further subsidence-transect surveys and organization of historical information are needed to continue verification of the rate of subsidence, In addition, this reduced rate of subsidence supports the premise that long-term agronomic, microbiological, physiological, hydrological, and genetic research focused on the maintenance of agricultural productivity while attempting to control subsidence mg prove successful.